Methods and materials for laser cladding

ABSTRACT

In a laser cladding, a diamond particulate is applied to the base material of an article that has been melted by an energy source such as a laser. The particulates are introduced into the molten material and allowed to settle as the article surface cools and solidifies. The diamond particulates function to increase the wear resistant characteristics of the article. In one embodiment, the diamond particulates are covered with a metallic veneer, which may be tungsten.

This utility patent application claims priority to U.S. provisionalpatent application Ser. 61/103,069 filed on Oct. 6, 2008, entitledMethods and Materials for Laser Cladding, which is incorporated hereinby reference in its entirety.

TECHNICAL FIELD

The present invention pertains generally to methods and materials usedin laser cladding metallic articles, and more particularly, toincorporating additives that improve the wear resistance of thearticles.

BACKGROUND OF THE INVENTION

Metal parts frequently fail their intended use, due not only tofracturing but also to wear and abrasion. Wear changes a metal partdimensionally and as such functionally. Processes are known forrepairing worn metal parts where durable material is adhered to theabraded surface. Laser cladding is one such process. The manufacturingsector also uses laser cladding to adhere hard material onto relativelysofter material for improved wear resistance and durability. In lasercladding, a concentrated beam of energy is impinged on the surface of agiven article melting an outer layer of material. A powder is theninjected or deposited onto the melted surface where the particulatescombine with the substrate.

BRIEF SUMMARY

In one embodiment of the subject invention, a method of cladding anassociated article includes the steps of directing a source of energyhaving enough power to melt at least a portion of an associated articleand infusing mineral granules into the at least a portion of theassociated article where the mineral granules may be diamonds orcorundum granules. In another embodiment of the subject invention amethod of laser cladding an associated metallic article includes thesteps of providing and activating a laser having a beam of energy thatimpinges the surface of the associated metallic article, directing thelaser along a trajectory thereby creating a molten puddle on a surfaceof the associated metallic article, and depositing non-metallic,crystalline particulates into the molten puddle where the non-metallic,crystalline particulates may be diamonds or corundum granules.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a laser melting the surface of a roundedarticle in accordance with the embodiments of the subject invention.

FIG. 2 is a perspective view of a laser melting the surface of a planararticle where diamond particulates are being added to the substrate inaccordance with the embodiments of the subject invention.

FIG. 3 is a side view of a laser cladding process depositing diamondparticulates into a substrate, in accordance with the embodiments of thesubject invention.

FIG. 3 a is a side view of a cladding process depositing diamondparticulates into a substrate using a welding power supply, inaccordance with the embodiments of the subject invention.

FIG. 4 is a perspective view of several wear resistance particulates,which may be diamond particulates, covered by a veneer, in accordancewith the embodiments of the subject invention.

FIG. 5 is a cross-sectional close up view of a wear resistantparticulate embedded in a substrate layer, in accordance with theembodiments of the subject invention.

FIG. 6 is a schematic representation of an article showing appliedcladding material having wear resistant particulates embedded therein,in accordance with the embodiments of the subject invention.

FIG. 7 is a block diagram of a method of increasing the wear resistantcharacteristics of an associated article, in accordance with theembodiments of the subject invention.

FIG. 8 is a block diagram of a method of laser cladding an associatedmetallic article, in accordance with the embodiments of the subjectinvention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings wherein the showings are for purposes ofillustrating embodiments of the invention only and not for purposes oflimiting the same, FIG. 1 depicts an energy source 10 used in claddingthe surface of an associated article 15. The energy source 10 maydeliver power in any of various forms as derived from for exampleelectrical current, and/or electromagnetic radiation in the form ofamplified light. In one embodiment, the energy source 10 is a laser 12,although other sources of energy like an arc welding power supply 16 maybe utilized without departing from the intended scope of coverage of theembodiments of the subject invention. The energy source 10 may directenergy onto the surface of the article 15 thereby melting an outer layerof material. The ensuing molten puddle 28 is then infused with one ormore substances for increasing the wear resistance of the article 15 aswill be discussed in detail below. In the solidified state, thesubstances, engrained into the substrate, function to resist abrasionand deterioration during use of the article 15.

Generally the embodiments of the subject invention pertain to metallicarticles, although similar methods may be used for non-metalliccomponents. Accordingly, article 15 may be comprised of a base metalsuch as iron and may be constructed from sheet steel, steel plate, orround stock. The methods and processes described herein may also beapplied to alloyed metals, like aluminum or any other alloy chosen withsound engineering judgment. Applications of the embodiments of thesubject invention include but are not limited to the repair orresurfacing of worn or damaged parts, the application of coatings oncomponent surfaces and additive manufacturing, to name a few.

With reference to FIGS. 1 and 2, laser 12, which may be a direct diodelaser 12, directs energy at a designated rate to melt an outer portionof article 15. The amount of material melted, i.e. its thickness ordepth, is dependant in part on the intensity of the energy beam 13 andits dwell time, along with other factors like the composition of thebase material. The laser 12 may traverse a pathway covering the articlesurface or select portions of the article surface. In one embodiment,the laser 12 may have characteristic beam width, which may be in therange between 0 mm and 15 mm. More specifically, the beam width may besubstantially 12 mm. However, it is to be construed that otherconfigurations of lasers, including but not limited to spot lasers, maybe utilized without departing from the intended scope of coverage of theembodiments of the subject invention. Accordingly, a trajectory may bechosen that takes into account the width of the beam 13, the power rateand the travel speed of the laser beam 13 relative to the surface ofarticle 15. Of course, persons skilled in the art will readilyunderstand that one or both of the laser 12 and article 15 may moverelative to the other at any rate suitable for melting a surface ofarticle 15.

In one particular embodiment of the subject invention, a shielding gas17 may be dispensed in conjunction with the laser beam 13. In thismanner, the surface of the article 15 may be shrouded or showered with agas 17, which may be an inert gas 17, to minimize interaction of themelt zone 18 with the atmosphere. Adverse phenomena, specifically theformation of a plasma cloud, can occur at the point of interactionbetween the laser beam 13 and the surface being treated. The plasmacloud absorbs and reflects part of the beam 13, and tends to defocus theremaining portion of the beam 13 thereby lessening its intensity.Accordingly, a flowing inert gas 17 is provided to flood the regionsurrounding the laser beam 13 and hence the melt zone 18. Examples ofgas 17 used include: Helium, Argon, and combinations thereof. However,the aforementioned list is not to be construed as limiting. Rather, anytype of gas may be used that effectively prevents the formation of aplasma cloud, as well as other adverse effects. The gas 17 may bedispensed from the same nozzle as that of the laser beam 13.Alternatively, a separate nozzle, not shown, may be used to dispense thegas 17 and flood the melt zone 18 in a manner consistent with thatdescribed above. Still, any means of dispensing a shielding gas 17 maybe chosen with sound engineering judgment.

With continued reference to FIG. 2 and now also to FIG. 3, a feeder 20may be used to deposit a substance or substances onto the surface ofarticle 15 for infusing with the molten material of article 15. In oneembodiment, the feeder 20 may use gravity to dispense the substances.The feeder 20 may incorporate one or more components that make up agravity feed mechanism. A tubular member 24 may be utilized that directsmaterial from a feed source, not shown, to a point in or near the moltenpuddle 28. The tubular member 24 may be adjustable with respect to itsposition behind the laser 12 or laser beam 13. It will be appreciatedthat the tubular member 24, also termed feed tube, may be positioned atany position relative to the melt zone 18 as is appropriate for use withthe embodiments of the present invention. Alternatively, the feeder 20may propel the substances onto the surface of the article 15 or injectthe substances into the molten puddle 28 by using a pressurized medium,like for example inert gas 17. Still, any device or method of dispensingsubstances used in the cladding process may be chosen without departingfrom the intended scope of coverage of the embodiments of the subjectinvention.

In one particular embodiment, multiple feeders 20 _(a), 20 _(b) may beused to dispense substances onto the surface of article 15. The feeders20 _(a), 20 _(b) may deposit the same or different materials. In anexemplary manner, feeder 20 _(a) may dispense a crystalline particulate,which may be diamond particulates 27, used to increased the wearresistant characteristics of article 15. Similarly, feeder 20 _(b) maydispense another particulate, which may include for example claddingparticulates or other matter suitable for use in the cladding process.The feeders 20 _(a), 20 _(b) may be positioned at various locations inrelation to the laser 12, and more particularly in relation to theimpinging beam 13 on the surface of article 15. In particular, thefeeders 20 _(a), 20 _(b) may be fixedly positioned with respect to thelaser 12 and, more specifically, may be rigidly connected to the laser12 by any suitable means chosen with sound engineering judgment. In anexemplary manner, feeder 20 _(a) may be positioned in front of beam 13,i.e. ahead of the laser beam 13 in relation to its direction of travel,while feeder 20 _(b) may be situated behind the beam 13. Still, thefeeders 20 _(a), 20 _(b) may be positioned at any location and distancefrom the beam 13 and/or melt zone 18 as chosen with sound engineeringjudgment.

With continued reference to FIGS. 2 and 3 and now also to FIG. 4, thesubstances dispensed from feeder 20 may function to increase the wearresistant characteristics of article 15. In one embodiment, thesubstances, referred to herein as wear resistant particulates 26, may becomprised of a mineral substance. It is contemplated in one embodimentthat the mineral substance may be substantially nonmetallic in nature;that is to say comprised mostly of elements that are categorized asnonmetallic. The wear resistant particulates 26 may also besubstantially elemental in its construction. Additionally, in its solidphase, the mineral substance may be crystalline in nature. Morespecifically, the microscopic configuration of the crystalline latticestructure may be configured isometrically, which is to say that thelattice structure is arranged in an array of points repeatingperiodically in three dimensions. In one embodiment, the wear resistantparticulates 26 may be comprised mostly of carbon atoms, which in theaforementioned configuration, is more commonly known as diamond 27. Itis known in the art that diamond substances are not necessarilycomprised completely or purely of carbon. Rather other elements may beinterspersed into the lattice structure like for example nitrogen, whichis known to give diamond substances a yellow hue. It is to be construedthat all such variations are to be included within the scope of coverageof the embodiments of the subject invention.

Other embodiments are contemplated wherein the wear resistantparticulates 26 are comprised of mineral substances including compoundsother than or in addition to diamond 27. Such mineral substances maysimilarly have a lattice structure that is isometrically configured. Onetype of mineral is made from Aluminum Oxide commonly called corundum.Examples of such wear resistant particulates 26 may include sapphires,rubies and the like. In this manner, the mineral substances may becharacterized as gemstones and may be substantially homogenous inconfiguration. Mineral substances such as those described herein mayinclude various quantities of foreign particulates, which may be encasedby the lattice structure or incorporated into the lattice structure.Again, all such compounds are to be construed as falling within thescope of coverage of the embodiments of the subject invention.

The wear resistant particulates 26 may be relatively small in diameterranging in size from approximately 100μ (microns or micrometers) up toand exceeding 800μ (microns or micrometers). More specifically, the wearresistant particulates 26 may be in the range substantially between 400μ(microns or micrometers) to 600μ (microns or micrometers). However, thewear resistant particulates 26 may be somewhat larger or smaller thanthe stated ranges. In an exemplary manner, the figures depict generallycircular or elliptically shaped particulates, although the wearresistant particulates 26 may also be elongate or have any shape as isappropriate for use with the embodiments of the subject invention.

With continued reference to FIGS. 4 and 5, another embodiment iscontemplated wherein the wear resistant particulates 26 may be at leastpartially covered or coated with a veneer 31. The veneer 31, or coating31, may be comprised of metal or metal alloy. The metal or metal alloymay itself be hard or wear resistant. Additionally, the materialcomprising the veneer 31 may correspond to the base material of article15. That is to say that the material comprising the metallic veneer 31may effectively blend together with the base material of article 15. Inone example, the veneer 31 is comprised of tungsten or tungsten carbide.Tungsten, once exposed to the energy source of the laser beam 13 and/orheat from molten puddle 28, melts forming a tungsten carbide substrate34 within which the wear resistant particulates 26 become embedded.Other embodiments are contemplated wherein the veneer 31 is comprised ofcobalt, chromium and/or alloys formed therefrom. Still, the veneer 31may be comprised of any metal as is appropriate for use with theembodiments of the subject invention.

With reference now to FIG. 6, in one embodiment, the type and/or amountof veneer 31 may be selectively adjusted to change the overall densityof the wear resistant particulates 26. In the example of diamondparticulates 27, it will be understood that diamonds 27 aresubstantially homogeneous having a generally uniform density. As such,uncoated diamond particulates 27 will penetrate only so far into themolten puddle 28 regardless of its size. To increase penetration intothe molten puddle 28, the amount of veneer 31 may be changed to increasethe overall density of the particulate 26 allowing it to settle deeperinto the molten puddle 28. In one example, the thickness of the veneer31 may range from just one micrometer up to 50 micrometers. However, anythickness of veneer 31 may be chosen as is appropriate for use with theembodiments of the present invention. It will also be realized that therate of cooling of the molten puddle 28 and its viscosity, which changeswith the distance from the melt zone, may affect how deep the wearresistant particulates 26 settle into the molten puddle 28. Accordingly,the position of tubular member 24 may be adjusted to achieve any desiredsettling depth of the wear resistant particulates 26. Persons of skillin the art will further appreciate that some of the wear resistantparticulates 26 may be manufactured having different veneer thicknesses,and thus different densities, than other wear resistant particulates 26.When combined and dispensed together, the wear resistant particulates 26settle at different depths. By adjusting the proportion of lighter toheavier density particulates, the end-user may effectively distributethe wear resistant particulates 26 through a range of depths within thesubstrate. All such proportions are to be construed as falling withinthe scope of coverage of the embodiments of the subject invention.

The invention has been described herein with reference to the disclosedembodiments. Obviously, modifications and alterations will occur toothers upon a reading and understanding of this specification. It isintended to include all such modifications and alterations insofar asthey come within the scope of the appended claims or the equivalencethereof.

1. A method of increasing the wear resistance an associated article,comprising the steps of: directing a source of energy having sufficientpower to melt at least a portion of an associated article; and, infusingmineral particulates into the at least a portion of the associatedarticle for increasing the wear resistance of the associated article. 2.The method as defined in claim 1, wherein the mineral particulates arecomprised of: diamond.
 3. The method as defined in claim 1, wherein themineral particulates are comprised of: corundum particulates.
 4. Themethod as defined in claim 1, wherein the associated article includes asurface area that is at least partially metallic; and, wherein thesource of energy is a source of electromagnetic radiation havingsufficient power to melt at least a portion of the metallic surface areaof the associated article.
 5. The method as defined in claim 4, whereinthe step of directing a source of energy comprises the step of:directing a source of energy having sufficient power to melt at least aportion of the metallic surface area thereby forming a molten puddle;and wherein the step of infusing mineral particulates, comprises thestep of: depositing mineral particulates into the molten puddle.
 6. Themethod as defined in claim 1, wherein the size of mineral particulatesrange from between 100 micrometers to 800 micrometers.
 7. The method asdefined in claim 1, wherein the size of mineral particulates range frombetween 400 micrometers to 600 micrometers.
 8. The method as defined inclaim 1, wherein the source of energy is amplified light.
 9. The methodas defined in claim 1, wherein the source of energy is derived from awelding power supply.
 10. A method of laser cladding an associatedmetallic article, comprising the step of: providing and activating alaser having a beam of energy that impinges the surface of theassociated metallic article; directing the laser along a trajectorythereby creating a molten puddle on a surface of the associated metallicarticle; and, depositing non-metallic, crystalline particulates into themolten puddle for increasing the wear resistance of the associatedmetallic article.
 11. The method as defined in claim 10, wherein atleast a portion of the non-metallic, crystalline particulates have anisometrically configured lattice structure.
 12. The method as defined inclaim 10, wherein the non-metallic, crystalline particulates arecomprised of diamond particulates.
 13. The method as defined in claim10, wherein the non-metallic, crystalline particulates are comprised ofcorundum particulates.
 14. The method as defined in claim 10, whereinthe non-metallic, crystalline particulates are deposited into the moltenpuddle at a location behind the beam of energy.
 15. The method asdefined in claim 14, wherein the location behind the beam of energy isin the range substantially between 0 inch and 1 inch.
 16. The method asdefined in claim 10, wherein at least some of the non-metallic,crystalline particulates are at least partially covered with a veneer.17. The method as defined in claim 16, wherein the veneer is comprisedof at least one of: tungsten, cobalt or chromium.
 18. A system for metalcladding, comprising: a laser having sufficient power to melt at least asurface portion of an associated metallic article; and, a feeder fordepositing diamond particulates.
 19. The system as defined in claim 18,wherein the feeder is fixed in positioned with respect to the laser fordepositing diamond particulates into a melted surface portion of theassociated metallic article; and further comprising: a second feeder fordepositing cladding particles onto an un-melted surface of theassociated metallic article.
 20. The system as defined in claim 19,further comprising: means for dispensing a gas for at least partiallycovering that region of the associated metallic article melted by thelaser.